Fossil carbon-based resources (oil, coal, gas) cover 85% of the world's energy needs and serve as starting materials for 95% of organic chemical consumables (plastics, fertilizers, pesticides, and the like). The dwindling of oil resources and the accumulation of CO2 resulting from their use thus present an ecological problem, an energy problem and a problem of availability of raw materials for the chemical industry. In this context, it is appropriate to provide novel routes for the synthesis of chemical consumables, so as to construct a lasting industry based on the use of renewable carbon-based resources.
To circumvent the petrochemical industry and to achieve the maximum recovery in value of its carbon-based waste, CO2, in order to produce organic molecules, such as polymers, fertilizers, synthetic textiles, and the like, thus represents a key scientific challenge. This is because the recycling of CO2 exhibits the twofold advantage of economizing on the fossil carbon-based resources (coal, hydrocarbons, and the like) normally used to synthesize organic molecules, while avoiding an increase in the emissions of this greenhouse gas.
However, the development of chemical reactions which make it possible to convert CO2, in particular by replacing all the C—O bonds of the CO2 with new C—H, C—C, C—N and C—S bonds, and the like, presents technical difficulties.
This is because, in view of the high thermodynamic stability of carbon dioxide, its conversion requires an external energy source so as to favor the thermodynamic balance of the chemical conversion and the use of catalyst to accelerate the reactions.
While CO2 is often proposed as carbon source for its recovery in value as intermediates in chemistry (Sakakura, T., Choi, J. C. and Yasuda, H., Chem. Rev., 2007, 107, 2365), the only reaction during which all the C—O bonds are split and new bonds are formed is the reduction of CO2 to give methane (A. J. Morris, G. J. Meyer and E. Fujita, Acc. Chem. Res., 2009, 42, 1983; A. Berkefeld, W. E. Piers and M. Parvez, J. Am. Chem. Soc., 2010, 132, 10660). All the other known processes result in molecules always exhibiting C—O and/or C═O bonds, resulting from CO2, with a partial reconstruction of the valency of the carbon (as in methanol, urea, formamides, and the like).
Mention may be made, as an example of conversion of CO2 into novel chemical consumables by using a reactive chemical partner (high energy) to promote the thermodynamic balance of the chemical conversion of CO2, of the industrial synthesis of urea obtained by condensation of ammonia with CO2 (Sakakura, T., Choi, J. C. and Yasuda, H., Chem. Rev., 2007, 107, 2365). This synthesis is shown in equation 1 below.

According to the same principle, the synthesis of polycarbonates by CO2/epoxides copolymerization is in the process of industrialization as shown in equation 2 below (Panorama des voies de valorisation du CO2 [Overview of the routes for recovering CO2 in value], ADEME, June 2010, http://www2.ademe.fr/servlet/getDoc?cid=96&m=3&id=72052 &p1=30&ref=12441).

In both these syntheses (equations 1 and 2), there is no formal reduction of the central carbon atom of the CO2. A C═O bond of each CO2 converted is retained in the final structure.
Still with the aim of obtaining novel chemical consumables, the strategy envisaged can consist in completely modifying the coordination sphere of the CO2 by replacing all the C—O bonds of the CO2 with novel bonds of the C—N, C—H, C—C, C—S and/or C—O type.
To date, the reduction of the CO2 to methane is the only catalytic process known for converting CO2 into a molecule in which the four C—O bonds of the CO2 have been replaced by four C—H bonds.
This strategy can also be applied in order to convert CO2 into nitrogenous compounds chosen, for example, from amidines, nitrogenous heterocycles, and the like, which are a class of important chemical compounds in the chemical industry, where they are commonly used as reactants, medicaments, pesticides, herbicides, antifungals, and the like.
Among the amidines, the formamidines of general formula R1NCHNR5R6 are generally synthesized by condensation of primary amines with formamides in the presence of a strong dehydrating agent, such as thionyl chloride (SOCl2), trichlorophosphate or trifluoroacetic anhydride (M. Gall, J. M. McCall, R. E. TenBrink, P. F. Von Voigtlander and J. S. Mohrland, Journal of Medicinal Chemistry, 1988, 31, 1816-1820; S. Enthaler, K. Schröder, S. Inoue, B. Eckhardt, K. Junge, M. Beller and M. Drieβ, European Journal of Organic Chemistry, 2010, #25, pp. 4893-4901; K.-M. Cheng, Y.-Y. Huang, J.-J. Huang, K. Kaneko, M. Kimura, H. Takayama, S.-H. Juang and F. F. Wong, Bioorganic and Medicinal Chemistry Letters, 2010, vol. 20, #22, pp. 6781-6784; A. Mekhalfia, R. Mutter, W. Heal and B. Chen, Tetrahedron, 2006, vol. 62, #24, pp. 5617-5625). These synthetic routes generally require moderate heating (60° C.) to strong heating (180° C.) and require the use of toxic reactants (SOCl2, POCl3, and the like).
An alternative route is based on the synthesis of formamidines by reaction between a primary amine and a trialkyl orthoformate which is generally (EtO)3CH or (MeO)3CH (Samad Khaksar, Seyed Mohammad Vandat, Akbar Heydari and Mahmood Tajbakhsh, Journal of Fluorine Chemistry, 2010, vol. 131, No. 12, pp. 1377-1381). Applied to diamines, this reaction is used for the synthesis of nitrogenous heterocycles, such as benzimidazoles, quinazolinones, 3,4-dihydroquinazolines, and the like.
In order to use CO2 as carbon source for synthesizing nitrogenous chemical compounds chosen, for example, from amidines, nitrogenous heterocycles, and the like, in which all the C—O bonds of the starting CO2 are replaced with novel bonds of the C—N, C—H and/or C—O type, it is necessary to overcome a technical challenge which consists in combining the functionalization of the CO2 with a stage of chemical reduction and a stage of deoxygenation. In order to maximize the energy yield of such a conversion, it is necessary to develop reactions with a limited number of stages (ideally just one) and which are catalyzed, in order to avoid energy losses of a kinetic nature.